Windows must be sealed from the elements in order to protect both the integrity of the window and the finished interior of a building. Traditionally, liquid sealants are used, such a silicone, as the means for managing air and water within the window system. Often silicone is applied in a thin strip, or applied with skips in the bead creating pin sized holes allowing water to penetrate to the interior of the building. Cured liquid sealants can shear or separate during product handling and are not visible, creating the opportunity for water to enter the building.
Additionally, in nearly all the current window glazing systems, at the corner joints, a bead of liquid sealant is placed along the profiled edge of the corner. This sealant bead is then compressed between the two frame members. The sealant is compressed to such a thin amount that if the window is handled poorly during transportation or installation, the sealant can shear or separate from itself. This will allow water to enter the frame and eventually enter the building.
A window system that is superiorly effective at sealing out the elements is desirable.